369  
FXUS66 KSEW 100312  
AFDSEW  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SEATTLE WA  
812 PM PDT WED JUL 9 2025  
   
UPDATE  
NO CHANGES MADE TO THE PREVIOUS FORECAST. WEAK  
CONVERGENCE CURRENTLY OVER SNOHOMISH COUNTY AS A FRONT IS WELL  
EAST OF THE CASCADES. LOWS TONIGHT ARE TO RANGE BETWEEN THE LOWER  
TO UPPER 50S WITH MOSTLY CLOUDY SKIES. THE PREVIOUS DISCUSSION  
REMAINS BELOW ALONG WITH AN UPDATED MARINE AND AVIATION SECTION:  
 
 
 
   
SYNOPSIS  
FRONT OVER CASCADES LATE THIS AFTERNOON WILL CONTINUE  
TO MOVE EAST. HIGH PRESSURE, BOTH AT THE SURFACE AND ALOFT,  
BUILDING OFFSHORE THURSDAY AND REMAINING IN PLACE INTO NEXT WEEK.  
UPPER LEVEL RIDGE STRENGTHENING TUESDAY AND WEDNESDAY WITH  
THERMALLY INDUCED SURFACE TROUGH MOVING UP THE COAST. THE  
RESULTING LOW LEVEL OFFSHORE FLOW COULD PUSH HIGHS INTO THE 90S  
OVER THE SOUTHERN PORTION OF THE INTERIOR WEDNESDAY.  
 
 
   
SHORT TERM /TONIGHT THROUGH SATURDAY/  
SATELLITE IMAGERY SHOWS  
CLOUDY SKIES OVER MOST OF THE AREA THIS AFTERNOON. A LITTLE  
DOWNSLOPE OFF THE OLYMPICS HAS CREATED CLEARING ON THE EAST  
SLOPES OF THE OLYMPICS. DOPPLER RADAR HAS SHOWERS MOSTLY CONFINED  
TO THE NORTHWEST INTERIOR AND CENTRAL AND NORTHERN CASCADES.  
TEMPERATURES AT 3 PM/22Z WERE IN THE 60S AND LOWER 70S.  
 
COLD FRONT OVER THE CASCADES THIS AFTERNOON WILL CONTINUE TO MOVE  
EAST. ONSHORE GRADIENTS INCREASING WITH CONVERGENCE ZONE  
DEVELOPING OVER SNOHOMISH AND EXTREME NORTHERN KING COUNTY BY LATE  
THIS AFTERNOON. THE CONVERGENCE ZONE WILL REMAIN IN PLACE THROUGH  
THE EVENING HOURS BEFORE DISSIPATING. UP TO ANOTHER TENTH OF AN  
INCH OF RAIN IN THE ZONE WITH THE HIGHEST AMOUNTS IN THE CASCADES  
AND CASCADE FOOTHILLS. FOR THE REMAINDER OF THE AREA SOME  
CLEARING OVER THE SOUTH PUGET SOUND IN RESPONSE TO THE CONVERGENCE  
ZONE OTHERWISE MOSTLY CLOUDY SKIES. LOWS TONIGHT IN THE 50S.  
 
HIGH PRESSURE, BOTH AND THE SURFACE AND ALOFT, BUILDING OFFSHORE  
THURSDAY. MARINE LAYER OVER THE AREA IN THE MORNING WILL DISSIPATE  
IN THE AFTERNOON WITH WEAKENING ONSHORE FLOW AND THE STRONG MID  
JULY SUN. THE CLOUDY MORNING WILL KEEP HIGH TEMPERATURES BELOW  
NORMAL, IN THE MID 60S TO MID 70S.  
 
NOT MUCH CHANGE TO THE PATTERN THURSDAY NIGHT THROUGH SATURDAY.  
UPPER LEVEL RIDGE REMAINING CENTERED OFFSHORE WITH LIGHT LOW LEVEL  
ONSHORE FLOW. WITH THE WEAK ONSHORE FLOW, MARINE LAYER ALONG THE  
COAST WILL HAVE A HARD TIME MOVING INLAND IN THE OVERNIGHT HOURS.  
TEMPERATURES ALOFT WITH THE RIDGE AXIS OFFSHORE WILL BE FAIRLY  
STEADY THROUGH THE PERIOD. MODEL 850 MB TEMPERATURES BOUNCING  
BETWEEN PLUS 14C AND PLUS 17C. THIS COMBINED WITH LIGHT ONSHORE  
FLOW WILL KEEP TEMPERATURES FROM GETTING TOO WARM FRIDAY AND  
SATURDAY. HIGHS OVER THE INTERIOR IN THE MID 70S TO MID 80S.  
AFTERNOON SEABREEZES WILL KEEP HIGHS ON THE COAST NEAR 70.  
   
LONG TERM /SUNDAY THROUGH WEDNESDAY/  
EXTENDED MODELS IN GOOD  
AGREEMENT WITH THE FRIDAY AND SATURDAY WEATHER PATTERN REMAINING  
INTACT FOR SUNDAY AND MONDAY.  
 
CHANGES START TO OCCUR TUESDAY WITH THE RIDGE OFFSHORE GAINING  
AMPLITUDE AND A THERMALLY INDUCED THERMAL SURFACE TROUGH MOVING UP  
THE PACIFIC NORTHWEST COASTLINE. BY WEDNESDAY THE THERMAL TROUGH  
WILL BE ALONG THE WASHINGTON COAST. TEMPERATURES ALOFT WARMING  
TUESDAY WITH MODEL 850 MB TEMPERATURES IN THE PLUS 18C TO PLUS  
21C. MORE WARMING WEDNESDAY AS THE RIDGE CONTINUES TO AMPLIFY WITH  
850 MB TEMPERATURES IN THE PLUS 21C TO 24C RANGE. WARMER  
TEMPERATURES ALOFT COMBINED WITH INCREASING LOW LEVEL OFFSHORE  
FLOW WILL GIVE THE AREA A SHORT HEAT WAVE. HIGHS TUESDAY IN THE  
INTERIOR UPPER 70S TO NEAR 90 WITH MID AND UPPER 70S ALONG THE  
COAST. ABOUT 5 DEGREES WARMER WEDNESDAY WITH 80S TO MID 90S  
INTERIOR AND 80S ALONG THE COAST. WHILE NOT A RECORD, THE CURRENT  
FORECAST HIGH OF 90 DEGREES FOR SEATTLE NEXT WEDNESDAY WOULD BE  
ONLY THE 5TH TIME IN 81 YEARS WITH A HIGH 90 DEGREES PLUS ON JULY  
16TH. HEATRISK SOLIDLY IN THE MODERATE CATEGORY BOTH DAYS FOR THE  
INTERIOR. THE HOT AND DRY WEATHER COULD ALSO PRODUCE SOME FIRE  
WEATHER HEADLINES. FELTON  
 
 
   
AVIATION  
NORTHWESTERLY FLOW ALOFT AS AN UPPER LEVEL TROUGH  
CONTINUES TO EXIT W WA THIS EVENING. SOUTH TO SOUTHWESTERLY WINDS AT  
THE SURFACE GENERALLY RUNNING 5-10 KTS WILL GRADUALLY EASE FURTHER  
OVERNIGHT TO 3-8 KTS. CLM AND HQM ARE MORE WESTERLY WITH HQM RUNNING  
SPEEDS SIMILAR WHILE CLM SEEING SPEEDS MORE IN LINE WITH 8-12 KTS  
WITH OCCASIONAL GUSTS. PAE SEEING MORE NORTHERLY WINDS, ALSO  
RESULTING FROM THE PUSH DOWN THE STRAIT.  
 
MAJORITY OF CIGS VERY BORDERLINE VFR/MVFR, SOME ON THE LOWER SIDE,  
SOME ON THE UPPER. PAE IS THE ONLY REPORTING IFR AS OF 7 PM PDT.  
WITH PLENTY OF MOISTURE AT THE LOWER LEVELS, CIGS EXPECTED TO  
DEGRADE TONIGHT WITH WIDESPREAD MVFR TO IFR CONDITIONS. CONDITIONS  
IMPROVING BY EARLY THURSDAY AFTERNOON WITH WIDESPREAD VFR EXPECTED  
AT THE MAJORITY OF TERMINALS, WITH THE EXCEPTION OF ALONG THE COAST.  
 
KSEA...CIGS BOUNCING BACK AND FORTH BETWEEN MVFR AND VFR THIS  
EVENING AND THAT MAY CONTINUE THROUGH AROUND 07-09Z BEFORE  
CONDITIONS FINALLY DEGRADE TO SOLIDLY MVFR. FURTHER LOWERING WILL  
GRADUALLY OCCUR WITH CIGS EXPECTED TO BOTTOM OUT BETWEEN 1500-2000  
FT JUST SLIGHTLY AFTER 12Z AND REMAIN THERE INTO THE LATE  
MORNING/EARLY AFTERNOON. SOME LIGHT DRIZZLE MAY BE POSSIBLE, BUT  
CONFIDENCE REMAINS LOW ENOUGH TO NOT INCLUDE IN TAF. VFR CONDITIONS  
WILL RETURN THURSDAY AFTERNOON.  
THURSDAY MORNING AFTER 14Z-15Z.  
 
SOUTHWESTERLY SURFACE WINDS 5-10 KT THIS EVENING, EASING A LITTLE  
BIT MORE OVERNIGHT AS DISCUSSED ABOVE. GUIDANCE HINTS AT NORTHERLY  
WINDS RETURNING AFTER 23Z THURSDAY.  
 
29/18  
 
 
   
MARINE  
A WEAK FRONT CONTINUES TO EXIT THE INLAND WATERS  
THIS EVENING. ANOTHER PUSH OF WESTERLIES DOWN THE STRAIT OF JUAN DE  
FUCA ALLOWS THE INHERITED SMALL CRAFT ADVISORY TO REMAIN IN EFFECT.  
WESTERLY PUSHES WILL CONTINUE TO OCCUR ACROSS THE STRAIT EACH  
EVENING, BUT AT THIS TIME LOOK TO REMAIN BELOW SMALL CRAFT CRITERIA.  
ANOTHER WEAK SYSTEM WILL MOVE ACROSS THE WATERS THURSDAY MORNING.  
FOLLOWING THIS SYSTEM, STRONG HIGH PRESSURE WILL BUILD OVER THE  
WATERS, AND WILL REMAIN THE DOMINANT SURFACE FEATURE INTO EARLY NEXT  
WEEK, ESTABLISHING NORTHWESTERLY FLOW OVER THE COASTAL WATERS. HIGH  
PRESSURE WILL WEAKEN SLIGHTLY ON SATURDAY INTO EARLY NEXT WEEK.  
GUIDANCE HINTS AT STEEP SEAS SUNDAY INTO EARLY NEXT WEEK, WITH SEAS  
BUILDING TO 7-9 FT AT 8-9 SECONDS.  
 
29/18  
 
   
FIRE WEATHER  
COOLER AND MORE MOIST CONDITIONS WILL BEGIN TO CEASE  
ON THURSDAY AS SKIES CLEAR AND CONDITIONS BEING TO WARM UP WITH A  
WEAK UPPER LEVEL RIDGE BUILDING OVER THE AREA. FRIDAY WILL BE THE  
WARMEST/DRIEST DAY THIS WEEK WITH RH VALUES DROPPING BACK INTO THE  
25 TO 35% RANGE OVER THE MOUNTAINS AND ACROSS THE INTERIOR LOWLANDS  
SOUTH OF PUGET SOUND. MORE ROBUST ONSHORE FLOW WILL HELP USHER IN  
MORE MOISTURE THIS WEEKEND DESPITE HIGH TEMPERATURES REMAINING IN  
THE 80S.  
 
WHILE THERE IS SOME MODEL DISCREPANCY, THERE IS CONSENSUS THAT A  
MORE ROBUST UPPER LEVEL RIDGE WILL BEING TO BUILD AND MOVE INTO THE  
AREA BY THE MIDDLE OF NEXT WEEK. MODELS ARE BEGINNING SHOW THE  
DEVELOPMENT OF A THERMAL TROUGH ALONG THE COAST, WHICH WOULD ALLOW  
FOR WINDS TO SHIFT TO OFFSHORE, PROMOTING MUCH DRIER AND WARMER  
CONDITIONS AS WELL AS SOME POTENTIAL BREEZY WINDS THROUGH THE  
CASCADE GAPS. THIS PATTERN WILL CONTINUE TO BE CLOSELY MONITORED AS  
WE APPROACH NEXT WEEK.  
 
62  
 
 
   
SEW WATCHES/WARNINGS/ADVISORIES  
 
WA...NONE.  
PZ...SMALL CRAFT ADVISORY UNTIL 5 AM PDT THURSDAY FOR CENTRAL U.S.  
WATERS STRAIT OF JUAN DE FUCA-EAST ENTRANCE U.S. WATERS  
STRAIT OF JUAN DE FUCA.  
 
 
 
 
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